Regensburg 2016 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 62: Methods in Computational Materials Modelling IV: Method development
MM 62.6: Vortrag
Donnerstag, 10. März 2016, 17:15–17:30, H53
Efficient "On-the-Fly" Calculation of Raman Spectra from Ab-Initio Molecular Dynamics: Application to Lithium-Sulfur Batteries — •Pouya Partovi-Azar1, Thomas D. Kühne2, and Payam Kaghaychi1 — 1Physical and Theoretical Chemistry, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany — 2Department of Chemistry, University of Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany
We present a novel computational method to accurately calculate Raman spectra from first principles. Together with an extension of the second-generation Car-Parrinello method to propagate maximally localized Wannier functions along with the nuclei, a speed-up of one order of magnitude can be obtained.
We have used this method to investigate the Raman spectra of (Li2S4)n, n=1,4,8 clusters which are believed to be the last intermediates in the S8 → Li2S transition in lithium-sulfur (Li-S) batteries during the discharge cycle. However, it is not fully established whether or not any other products coexist with the Li2S crystal in the discharged state. In this study, we have observed a clear evidence of Li2S4 → Li2S2 transition by investigating the systematic changes in the simulated Raman spectra as the cluster size increases. In line with recent experiments, we found that the Raman-active sulfur-sulfur stretching mode at 440 cm−1 can be considered as a signature of covalent bonding between two and more sulfur atoms per formula. We have also demonstrated that the transition is mainly due to the strong electrostatic interactions between polar Li2S4 monomers.